EP4094117A1

EP4094117A1 - Augmented reality contact lens and corresponding method

Info

Publication number: EP4094117A1
Application number: EP21700962.0A
Authority: EP
Inventors: Jean-Louis De Bougrenet De La Tocnaye; Vincent NOURRIT; Kevin Heggarty
Original assignee: Institut Mines Telecom IMT
Current assignee: Institut Mines Telecom IMT
Priority date: 2020-01-21
Filing date: 2021-01-21
Publication date: 2022-11-30
Also published as: US11947118B2; WO2021148548A1; JP2023510222A; FR3106419A1; CN115039013A; US20230023682A1; KR20220126722A

Abstract

The augmented reality contact lens (100) comprises: - a transparent body (102) designed to be placed over one eye (104); and - at least one augmented reality module comprising an optical source (114) attached to the transparent body (102) and designed to emit light into the transparent body, and an optical element (116) attached to the transparent body (102) and designed to receive the light from the optical source (114) and direct it towards the eye (104). The optical element (116) is a hologram designed to diffract the received light towards the eye (104) in the form of a holographic image.

Description

AUGMENTED REALITY CONTACT LENS AND METHOD

CORRESPONDING

The present invention relates to a contact lens for augmented reality and a corresponding method. [0002] By augmented reality, we understand the fact of superimposing an image representing text, a symbol, or a drawing, etc., on a real scene captured by the eye. Augmented reality is the basic premise of Extended Reality (XR), as well as Mixed / Merged Reality (MR). As an example of an augmented reality device, the American patent published under the number US 8,786,675 B2 describes a contact lens for augmented reality comprising: a transparent body designed to be placed on an eye; an optical light source attached to the transparent body and adapted to emit light into the transparent body; and an optical element attached to the transparent body and adapted to receive light from the optical source and send it towards the eye.

[0004] In this document, the optical light source consists of an array of pixels. In a particular embodiment, the contact lens has a mirror to reflect light back to the optical element which is a converging lens, so that the image of the pixel array is focused on the retina of the eye.

[0005] This assembly has the drawback of being relatively complex to implement. It is bulky and can present optical alignment problems with the risk of obscuring the user's vision of their surroundings.

The patent application published under the number JP2005311823 describes a contact lens in which a matrix of pixels is generated by means of an optical guide comprising a plurality of optical lines and an optical source suitable for illuminating the optical lines. Each pixel of the matrix is activated by locally applying an electric field through electrodes so as to locally modify the refractive index of the optical line. The contact lens further comprises a hologram configured to converge the light rays emitted by the matrix of pixels in the center of the pupil of the eye in order to achieve Maxwellian illumination.

[0007] Again, this assembly has the disadvantage of being relatively complex to implement. It is bulky and can present optical alignment problems with the risk of obscuring the user's vision of their surroundings.

[0008] It may thus be desirable to provide a contact lens for augmented reality which makes it possible to overcome at least some of the aforementioned problems and constraints. [0009] A contact lens for augmented reality is therefore proposed, comprising: a transparent body designed to be placed on an eye; an optical light source attached to the transparent body and adapted to emit light into the transparent body; and - an optical element attached to the transparent body and designed to receive light from the optical source and send it towards the eye; characterized in that the optical element is a hologram designed to diffract received light as a holographic image towards the eye.

[0010] Thus, the optical source can be very simple and compact because it does not have to create an image, unlike a matrix of pixels, but simply to emit light. Indeed, according to the invention the image is created by the hologram. In particular, such an optical source can be significantly more compact than a matrix of pixels.

[0011] Optionally, a contact lens for augmented reality according to the invention can also include all or parts of the following characteristics taken alone or in combination: the optical source is monochromatic and / or point; the contact lens further includes an optical guide configured to guide light from the optical source to the hologram; the optical guide comprises a transparent substrate and a layer of reflective material covering an outer surface of the transparent substrate; at least one of the optical source and the hologram is arranged inside the transparent substrate so as to be partially or completely surrounded by the transparent substrate; the contact lens comprises: a radio receiver attached to the transparent body and adapted to receive a command; and a module for selective activation of the augmented reality module as a function of the command received; the selective activation module comprises an index modification device designed to modify a refractive index of the optical guide in order to modify the illumination of the hologram so that the latter ceases to provide the holographic image; the selective activation module is designed to deactivate the optical source; and the contact lens has a central area formed only of the transparent body.

[0012] An augmented reality method is also proposed comprising: placing a transparent body of a contact lens on one eye; the emission of light into the transparent body from an optical source attached to the transparent body; and - receiving light by an optical element attached to the transparent body and sending the light towards the eye through the optical element; characterized in that the optical element is a hologram and in that the light sent to the eye is light diffracted by the hologram in the form of a holographic image.

The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the accompanying drawings in which:

[0014] [Fig. 1] FIG. 1 is a cross-sectional view of an augmented reality contact lens according to the invention, and of an eye on which it is placed; [0015] [Fig. 2] Figure 2 is a rear view of the augmented reality contact lens of Figure 1, i.e. when this contact lens is viewed from the eye;

[0016] [Fig. 3] Figure 3 is a view similar to Figure 1, where the elements of the contact lens are more detailed;

[0017] [Fig. 4] FIG. 4 is a functional view of an electronic module for controlling optical sources of the contact lens of the preceding figures;

[0018] [Fig. 5] Figure 5 is a flowchart describing an augmented reality method according to one embodiment of the invention; [0019] [Fig. 6] Figure 6 is a rear view of an augmented reality contact lens according to an alternative embodiment of the invention; and

[0020] [Fig. 7] Figure 7 is a sectional view of the contact lens of Figures 1 to 3 or of Figure 6, when encapsulating an augmented reality device in a transparent body of the contact lens. Referring to Figure 1, a contact lens 100 for augmented reality according to the invention will now be described.

The contact lens 100 is designed to be applied to an eye 104 having an optical axis AO and a visual axis AV intersecting at a point O. As is known per se, the eye 104 has everything of first a cornea 106 in the form of a spherical cap at the interface with the ambient air. The eye 104 further comprises an iris 122 pierced in its center by a circular opening called the pupil 123 through which the light is transmitted. The iris 122 expands or contracts depending on the light intensity. The eye 104 further comprises a lens 118 formed by a fibrous, transparent and flexible disc to focus the incident light received through the pupil 123. The point of intersection O is generally located approximately in the center of the lens 118. Behind the eye crystalline 118, on the other side of an ocular cavity 109, the eye 104 further comprises a retina 110 formed of sensory cells comprising cones for day vision and rods for night vision. The retina 110 presents a central zone, called fovea 111, in the extension of the visual AV axis, where the vision of details is most precise. The fovea 111 is thus eccentric by a few degrees relative to the optical axis AO. The retina 110 also has, around the fovea 111, an area, called parafovea 112, corresponding to peripheral vision. As can be seen in FIG. 1, the cornea 106, the pupil of the iris 122 and the lens 118 are substantially centered on the optical axis AO.

[0023] The contact lens 100 firstly comprises a transparent body 102 designed to be placed on the eye 104. [0024] The transparent body 102 has the shape of a disc curved around a central axis AC with a face concave rear 1004 and a convex front face 1003. The rear face 1004 has a shape complementary to the cornea 106 in order to be pressed against the cornea 106, in a privileged position of the contact lens 100 illustrated in FIG. 1. In this privileged position, the contact lens 100 is centered on the optical axis AO, so that the central axis AC of the transparent body 102 is substantially coincident with the optical axis AO.

As the transparent body 102 comes into contact with the cornea 106, it is made of a biocompatible material, for example based on silicone hydrogel or H EMA (Hydroxy Ethyl Methacrylate) or any other suitable material as described by C. Stephen, A. Musgrave and F. Fang in the article entitled “Contact Lens

Materials: A Materials Science Perspective ”published in the journal Materials, Vol. 14, 261, January 2019.

The contact lens 100 further comprises an augmented reality device 107 encapsulated in the transparent body 102 of the contact lens 100.

Referring to Figure 2, the augmented reality device 107 will now be described in more detail.

The augmented reality device 107 has for example the general shape of a flat crown or of a flat ring having a center located on the central axis AC of the transparent body 102. The augmented reality device 107 comprises a transparent substrate 105 intended to guide the light as will be explained later. The transparent substrate 105 comprises for example a liquid crystal.

The augmented reality device 107 further comprises at least one augmented reality module 108. In the example illustrated in FIG. 2, the augmented reality modules 108 are eight in number and distributed in a star, so that each augmented reality module 108 is aligned along a branch of the star. The augmented reality device 107 further comprises a control module 10 of the augmented reality modules 108, fixed to the transparent substrate 105. This control module 10 will be described in more detail later, with reference to FIG. 5. Each augmented reality module 108 is designed, once the contact lens 100 is in its privileged position on the eye 104, to generate an image on the retina 110, superimposed on a real scene captured by the eye 104 In the example described, the image is a warning sign intended to appear in peripheral vision. Thus, in the example described, the image is preferably generated on the parafovea 112. In addition, still in the example described, each augmented reality module 108 is designed to provide a different image on the retina 110. Thus, in this example, it is possible to display up to eight different images on the parafovéa 112.

[0032] The augmented reality modules 108 are similar to each other so that only one of them will now be described in more detail.

[0033] The augmented reality module 108 first comprises an optical source 114 attached to the transparent substrate 105 and designed to emit light into the transparent substrate 105.

Preferably, the optical source 114 is point, that is to say for example that it has a light output of dimension less than 100 μm, and monochromatic, that is to say for example that the light which it emits exhibits a single emission peak in wavelength, having a width at half-height of at most 100 nm. This peak is located in visible light, approximately 400 - 750 nm, and preferably in green or red: 500 - 670 nm. Alternatively, the peak is in the sensitivity wavelengths of the photoreceptors of the retina 110, and more particularly of the parafovea 112 (for example 420 nm for the rods and 534 nm for the M-cones).

More preferably, the optical source 114 has a divergence of less than 40 °. For example, the optical source 114 comprises a laser and more particularly at least one vertical cavity laser diode with surface emission called VCSEL (Vertical-Cavity Surface-Emitting Laser). Indeed, advantageously, this type of optical source has a reduced size, thus allowing to substantially reduce the thickness of the contact lens 100, compared to the pixel arrays used in the contact lenses of the prior art.

The augmented reality module 108 further comprises a hologram 116 fixed to the transparent substrate 105 and designed to receive the light from the optical source 114 and send it towards the eye 104, and more precisely towards the lens. 118 through the pupil 123. The hologram 116 is a diffractive optical element generally designated by the acronym DOE (from the English: Diffractive Optical Element). Thus, the hologram 116 is designed to diffract the received light, in the form of a holographic image in the direction of the eye 104. This transformation is based on the phenomenon of optical diffraction, so that the diffracted light (the image holographic) corresponds for example to the Fresnel or spatial Fourier transform of the final image that is to be imaged on the retina 110. Preferably, the tissues crossed by the light are taken into account in the design of the hologram . [0038] Thus, generally, the hologram 116 is configured to create and project the desired final image on the retina of the eye. In particular, the structure of the hologram defines this image. As previously noted, in some embodiments, the hologram can be configured to provide the spatial inverse Fourier transform of the final image to be projected onto the retina. In other embodiments, the hologram can be configured to implement an additional optical function such as the Fresnel transform of the desired image.

In practice, the hologram 116 comprises for example a transparent substrate plate of constant thickness, such as a glass plate, on or in which are profiled microstructures or nanostructures configured to diffract the incident wavefront so as to generate the holographic image. These microstructures or nanostructures form a diffraction pattern. Alternatively, instead of operating in transparency, the hologram 116 could operate in reflection and be in the form of a reflecting mirror. For example, the hologram 116 is obtained by depositing a layer of photosensitive resin (for example of type S 1813) with a thickness approximately equal to 1.2 μm, on the surface of the transparent body 102, in an area located opposite one end of the pupil 123, when the contact lens 100 is in its privileged position on the eye 104. A phase profile with multi-level phase is then photo- inscribed in the resin, the regions surrounding the hologram 116 being fully exposed. During a development step, the hologram 116 is etched in the resin layer, the resin around the hologram 116 being removed. The hologram 116 thus obtained has, for example, a resolution of approximately 750 nm with an etching depth of approximately 1000 nm.

So as not to disturb the central vision of the eye 104, the contact lens 100 preferably has a central zone 120 formed only of the transparent body 102. This central zone 120 is located on the optical axis AO, in front of the pupil 123, when the transparent body is placed on the eye 104 in its privileged position. By virtue of this central zone 120, the pupil 123 is at least partially free of any element that could degrade vision.

In particular, in the example described, the holograms 116 of the various augmented reality modules 108 are arranged in a ring around the central zone 120. This ring of holograms 116 has its greatest radius equal to the mydriasis (maximum opening of the pupil, for example, 8 mm) and its smallest radius such that the central zone of the pupil 123 is free (for example, 2 mm), which means that the pupil 123 can vary between these two values. Thus, each hologram 116 has, in the example described, a radial dimension of at most 6 mm. In the case where the pupil 123 is equal to the minimum radius of the holographic crown, no projection can be done on the retina 110. Otherwise, an image will always be formed on the retina, even if the hologram 116 is not is only partially cleared, because in this case the holographic image of at least part of the patterns of the hologram 116 still crosses the pupil 123, which is sufficient, by the design mode of said hologram, to allow the 'appearance of a final image on the retina 110, nevertheless in return for a reduction in the level of illumination of the retina 110. In fact, the hologram 116 comprises a periodic pattern so that if a part of it is obscured by the pupil 123, the hologram 116 makes it possible to create a holographic image which is always imaged on the retina 110 via the lens 118 but with a reduced intensity and possibly with a reduced resolution compared to the case where the hologram 116 n is not partial ent obscured by the pupil 123.

Referring to Figure 3, the central zone 120 preferably has a diameter d around the central axis AC of at least 3 mm in order to clear the pupil 123. To prevent part of the light emitted by the optical source 114 from leaving the transparent substrate 105 before reaching the hologram 116, the contact lens 100 further comprises a layer of reflective material 124 covering at least partly the surface of the transparent substrate 102, with the exception of the central zone 120 so as not to obscure the central vision of the eye 104. Thus, the transparent substrate 105 and the layer of reflecting material 124 form an optical guide guiding light from optical source 114 to the associated hologram 116.

Outside the central zone 120, the layer of reflective material 124 does not necessarily extend over the rest of the surface of the transparent substrate 105. For example, a periphery 1001 of the transparent substrate 105 may be devoid of any layer of reflective material 124.

[0046] For example, the layer of reflective material 124 includes gold. In this case, a very fine reflective layer of the order of a few nanometers can advantageously be produced by photo-lithographic technique, for example of the "lift-off" type.

[0047] Alternatively, the layer of reflective material 124 comprises aluminum or silver, which advantageously makes it possible to strengthen the strength and the reflectivity of the layer of reflective material 124.

As can be seen in Figure 3, the optical source 114 and the hologram 116 are arranged inside the transparent substrate 105, so as to be partially surrounded by the transparent substrate 105 and flush with the latter. Alternatively, one or both could be completely surrounded by the transparent substrate 105.

Referring to Figure 4, an embodiment of the control module 10 will now be described in more detail.

The control module 10 firstly comprises an electrical power source 130, such as a battery 130. The electrical power source 130 is in particular designed to power the optical source 114 of each reality module. increased 108. The control module 10 further comprises means for recharging the battery 132, for example of the inductive type.

The control module 10 further comprises an Rx radio receiver, for example Wi-Fi, designed to receive C commands. The contact lens 100 further comprises a module 136 for selective activation of the augmented reality module 108 as a function of the command received C. For example, the selective activation module 136 comprises a switch 1361 connected between the battery 130 and the optical source 114. Referring to FIG. 5, an example of an augmented reality method 500 will now be described.

This method more precisely describes the use of one of the augmented reality modules 108, but can be applied to each of the augmented reality modules 108. [0056] During a step E1, the contact lens 100 is placed on the eye 104 so that the transparent body 102 and more precisely its rear face 1004 is placed on the cornea 106, in the privileged position as illustrated in Figures 1 and 3.

[0057] It is initially assumed that the augmented reality module 108 is not activated, so that it does not provide a holographic image.

During a step E2, the selective activation module 136 receives, via the receiver Rx, a command C indicating the activation of the augmented reality module 108.

During a step E3, in response to the command C, the selective activation module 136 activates the augmented reality module 108 indicated in the command C so that the latter provides a holographic image. In the example described, the switch 1361, which was initially in the open position, is closed so that the electric power source 130 supplies the optical source 114. During a step E4, the optical source 114 , now powered, emits light which is guided inside the transparent body 102, by optical reflection between the layers of reflective material 124.

During a step E5, the hologram 116 associated with this optical source 114 receives the guided light. During a step E7, the hologram 116 diffracts the light received to form a holographic image sent in the direction of the eye 104, and more precisely in the direction of the pupil 123. In Figure 3, a light ray has been shown in dotted lines, so as to materialize the path of the light in a simplified manner. In reality, a plurality of light rays are emitted by the optical source 114, so as to form a light beam. During a step E9, the lens 118 receives the wave diffracted by the hologram and participates in the reconstruction of a final image (corresponding to this holographic image) on the retina 110.

Thus, the final image of the virtual object appears on the retina 110 where it is superimposed on the real scene captured by the eye 104. In the example described, the optical reconstruction takes place in the parafovea 112 for that the final image appears in the peripheral vision of the eye 104.

More precisely, the image of the virtual object is projected at approximately 10 ° from the fovea 111 (or else, which is equivalent, from the optical axis AO) with respect to the point O to avoid disturbing the central vision, which corresponds to 12-15 ° of the optical axis AO with respect to the point O. Preferably, the final image extends over at most 2 ° of field of view (approximately four full moons), this which corresponds to a length of approximately 1.15 mm on retina 110. At such a distance from fovea 111, neural resolution is significantly reduced compared to fovea 111, so that the smallest details in the image final should be at least 48 microns to be perceived.

During a step E10, the selective activation module 136 receives, via the receiver Rx, a command C indicating the deactivation of the augmented reality module 108.

During a step E11, in response to the command C, the selective activation module 136 deactivates the augmented reality module 108 indicated in the command C so that the latter no longer provides the holographic image. In the example described, the switch 1361 is opened so that the power source 130 no longer supplies the optical source 114 and the latter stops emitting light. Referring to Figure 6, a 100 ’contact lens according to an alternative embodiment of the invention will now be described.

This variant embodiment differs essentially from the previous embodiment described above on the number of augmented reality modules (four at instead of eight) and how holograms intended to be sent to the eye are selectively turned on and off.

According to this variant embodiment, the optical sources 114 emit light continuously and the selective activation module 136 comprises, for each hologram 116, an index modification device 140 designed to modify a refractive index of the transparent substrate 105, for example by means of the liquid crystal that it contains. Indeed, this liquid crystal is a birefringent electro-optical component whose index is modified by the application of an electric field. Once the index is changed, the guiding conditions (eg, the angle of deflection) are changed so that the hologram 116 is no longer illuminated to provide the holographic image.

[0072] For example, the index modifier 140 includes at least one pair of electrodes designed to generate the electric field changing the index of refraction, at least in one direction. In the example described, these electrodes are produced by plates of reflective material 124. More precisely, the reflective material 124 comprises, on a front face of the transparent substrate 105, a large ring 124A and, on a rear face of the transparent substrate 105 , a small ring 124B. This small ring 124B is divided into four segments 142A, 142B, 144A, 144B electrically isolated from each other and connected to the controller 10 '. Each pair of opposing segments forms a pair of electrodes.

Thus, on receipt of a command C, the selective activation module 136 is designed to apply a voltage between the electrodes associated with the augmented reality module 108 concerned by the command C, in order to modify the refractive index of the transparent substrate 105 extending between the electrodes. Thus, the hologram 116 of the augmented reality module 108 is no longer adequately illuminated to provide the holographic image.

Referring to Figure 7, the transparent body 102 comprises for example a base 102A having a housing 702 for receiving the augmented reality device 107 or 107 ', as well as a cover 102B designed to cover the base and the device. of augmented reality 107 or 107 'received in housing 702.

From the previous description, it is understood that it is the hologram which creates the holographic image, when it is illuminated by the optical source. In this case, the optical source provides neutral light having no image or image information (eg, a beam of light of uniform intensity). So, the hologram illuminated only by the optical source is capable of creating an image in the direction of the eye. Unlike the techniques of the prior art, no screen or matrix of pixels is necessary. In particular, the optical source can be as simple as a point source illuminating the hologram alone. It clearly appears that a contact lens for augmented reality such as those described above makes it possible to superimpose on the retina of the eye an image of a real scene captured by the eye, in a compact and simple manner.

It will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to him.

In particular, the nature and the emission properties of the optical source can be adapted depending on the intended application.

[0079] Additionally, an optical element, for example a Fresnel lens, could be placed between optical source 114 and hologram 116 in order to shape the beam to improve imaging conditions.

In the detailed presentation of the invention which is given above, the terms used should not be interpreted as limiting the invention to the embodiments presented in the present description, but should be interpreted to include all the equivalents including forecasting is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

[1] A contact lens (100; 100 ’) for augmented reality comprising: a transparent body (102) designed to be placed over an eye (104); at least one augmented reality module (108) comprising: · an optical source (114) fixed to the transparent body (102) and designed to emit light into the transparent body (102);

• an optical element (116) attached to the transparent body and designed to receive light from the optical source (114) and send it towards the eye (104); characterized in that the optical source (114) is adapted to emit light, received by the optical element (116), having no image and in that the optical element (116) is a hologram adapted to diffracting the received light to create a holographic image towards the eye (104).

[2] A lens according to claim 1 comprising a plurality of augmented reality modules (108), each module (108) being designed to provide a different final image on the retina (110).

[3] A contact lens (100; 100 ’) according to claim 1 or 2, wherein the optical source (114) is monochromatic and / or point.

[4] A contact lens (100; 100 ') according to one of claims 1 to 3, further comprising an optical guide (105, 124) adapted to guide light from the optical source (114) to the hologram ( 116).

[5] A contact lens (100; 100 ’) according to claim 4, wherein the optical guide comprises a transparent substrate (105) and a layer of reflective material (124) covering an outer surface of the transparent substrate (105).

[6] A contact lens (100; 100 ') according to claim 5, wherein at least one of the optical source (114) and the hologram (116) is disposed within the transparent substrate (105) in such a manner to be partially or else completely surrounded by the transparent substrate (105).

[7] Contact lens (100; 100 ') according to any one of claims 1 to 6 comprising: a radio receiver (Rx) fixed to the transparent body (102) and adapted to receive a command (C); and a selective activation module (136; 136 ') of each augmented reality module (108) as a function of the received command (C).

[8] A contact lens (100; 100 ') according to any one of claims 4 to 6 taken together with claim 7, in which the selective activation module (136') comprises an index modification device ( 140) designed to change a refractive index of the optical guide (105, 124) to change the illumination of the hologram (116) so that the latter ceases to provide the holographic image.

[9] A contact lens (100; 100 ’) according to claim 8, wherein the selective activation module (136) is adapted to deactivate the optical source (114).

[10] A contact lens (100; 100 ’) according to any one of claims 1 to 9, having a central area (120) formed only of the transparent body (102).

[11] Augmented reality method (500) comprising: - fitting (E1) of a transparent body (102) of a contact lens (100) on one eye (104); the emission (E4) of light in the transparent body (102) by an optical source (114) attached to the transparent body (102); and receiving (E5) the light by an optical element (116) attached to the transparent body (102) and sending (E7) the light towards the eye (104) by the optical element (116) ; characterized in that the light emitted by the optical source (114), and received by the optical element (116), has no image and in that the optical element (116) is a hologram diffracting the received light to create a holographic image in the direction of the eye (104).